Petrol engines
Before I start rambling about all the petrol engines I have to mention a very common problem related to the coolant reservoir which can crack and leak coolant, so be prepared to replace the coolant tank if it was not replaced in the past.
4.2 V8
From the petrol engines the most reasonable choice is the 4.2 l V8 with 335 hp. The reliability of this older engine is not that bad so with proper maintenance it can last a long time even though it has a couple of specific issues:
-the intake manifold plastic linkage will break at some point, but you can buy aftermarket mettalic linkages (link for the best quality linkages, but you can find them cheaper too)
-the cam chain tensioners can be worn usually after 200 000 km or 230 000 km which is not positive since you can end up with bent valves and shit if you dont replace them in time
-the infamous oil cooler or in other words oil filter housing pipe leak. Long story short a small plastic coolant pipe will crack and leak coolant and fixing this is not the easiest job. But you can buy an aftermarket mettalic tube which is gonna last forever (link for the best quality tube, but on ebay you can find it cheaper too)
The 3.7 l V8 engine can have the exact same issues as this 4.2 l V8.
6.0 W12
The biggest petrol engine is the second best petrol engine choice. It’s powerful enough and it doesn’t have any major problems – so with proper maintenance it can last a long time as well. But you should definitely keep bigger amount of money for the maintenance of this unit, since there is no space around the engine – so replacing certain parts or fixing some leaks will require either a lot of disassembling and a bit of creativity or removing the whole engine completely without being creative. It’s not easy to replace some basic things like the: alternator, starter, accessory belt, pulleys, water pump or some hoses → so for all of this shit you either remove “only some parts and be a bit creative”, or remove the whole engine. Obviously the fuel consumption of this unit is not small, but it’s a W12 so that should not be a surprise.
3.0 V6
The 3.0l V6 is essentially not the worst engine in the world, but I would avoid it since it is rare and not very powerful + it also doesn’t have the best reputation. In other words, issues with the catalytic converters, camshaft adjusters, misfires, oil consumption, and even cracked cylinder heads or cracked engine block can occur + adjusting the timing belt after replacing it is not the easiest + on early versions of this engine: the camshafts and the cam followers can be more worn too → mainly if the previous owner did long oil change intervals. Of course I’m not saying that this is a horrible engine and it can’t whitstand 300 000 km or more, but it’s just simply not worth it.
Direct injection engines
After this there are only the newer direct injection engines. They can have more often issues with faulty injectors, carbon build up, faulty camshaft adjustment solenoids or leaking seals on them + there are also the high pressure fuel pumps which will sooner or later leak fuel externally or rarely fail-causing bad/rough engine start and rough idle.
high pressure fuel pump fuel leak location video
2.8 FSI, 3.2 FSI
The 2.8 FSI and the 3.2 FSI are actually not bad engines, so except the usual direct injection issues, leaking high pressure fuel pump and some other leaks they are usually fine.
4.2 FSI
On the other side the 4.2 l FSI can have issues with the direct injection related stuff and also with the intake manifold plastic flaps which will get stuck, break and fall apart usually after 200 000 km or 250 000 + there are 2 electric flap actuators which can fail too. However cars made from 2009 (very late 2008) have an updated more simpler plastic intake manifold which should not cause issues. /the old problematic intake manifold is made from magnesium, the newer reliable is made from plastic/
Then various oil and coolant leaks also gonna appear on various spots of this engine, and to fix some of them you have to remove the whole engine.
S8 5.2 FSI V10
Last but not least there is the fantastic S8 version which has a fantastic 5.2 l V10 FSI engine which can have fantastic issues. I mean holy shit, I would rather have some engine powered by squirrels or hamsters, but lets fuckin start with the list:
-the direct injection related issues are gonna occur
-the complex variable intake manifold will have the same issues as described earlier, but in this case it can fail usually earlier = so even at around 100 000 km. That’s why before buying it’s good to open the hood and check for a rattling noise from the intake manifold mostly from 1000 up to 1500 RPM. This rattle indicates excessive play or broken bits in the intake manifold flap mechanism.
–oil leaks are gonna sooner or later appear on this engine too, so in this case you have to be also ready to remove the whole fucking engine to fix some of them + there is some coolant hose fitting at the rear of the engine which will disintegrate and leak coolant, but I can’t be bothered to find out more about this. So all in all, you have to expect oil and coolant leaks which are not gonna be always easy to fix.
-this engine has 4 catalytic converters and 8 O2 sensors which is awesome since all of this shit is gonna break, mainly if you have leaking injectors. And the funniest thing is that because of the lack of space you have to remove the engine to replace all the O2 sensors. Also because of the lack of space replacing other certain parts will require either a lot of disassembling around the engine or removing the whole engine completely. For example: the dealer is gonna remove the whole engine to replace the starter, but an independent mechanic can replace the starter without engine removal.
+ there is a bonus issue related to excessive oil consumption which can be caused by the damaged cylinder walls. So there are numerous cases when the engine block was replaced because of this even under warranty. On the other side this is not extremely common and some say that the engines made from 2008 don’t really have this issue anymore because they improved them, they say. I’m not interested in finding the complete truth in this, so do with this information whatever you want. All in all, a reasonable amount of oil consumption is acceptable, but if your engine consumes 1L of oil every 1 000 km then there is a very high chance that the cylinder walls are damaged. + A faulty PCV valve can cause excessive oil consumption too ! So if you got oil consumption then first check the PCV !!
Coolant leak which can kill the 4.2 FSI and 5.2 FSI engines
The rear timing chain covers of these engines do have a hole in them thru which the coolant flows. This would be fine, but it’s not. It’s not fine, since the coolant seal on these covers can fail and let the coolant leak directly into the engine-into the oil. Long story short: If you don’t catch this early then you will end up with a destroyed engine.
“All petrol engines: the exhaust flexible pipe will break at some point so check it before buying.”
“All petrol engines: expect vacuum leaks and faulty PCV.”
Diesel engines
From the diesel engines the most reasonable choice is the 3.0 TDI, but the 4.2 TDI is not a bad engine either mainly if you have a bit more money for the repairs. Both of these units can easily reach 400 000 km or 500 000 km, however they will have some issues:
-First, there are the variable intake manifold flaps which can fail. In this case you get only a check engine light, so the car will drive fine. The flaps can be stuck, loose or the actuator motors can be faulty.
-Then on the 3.0 l TDI it’s also good to check and eventually replace the crankshaft pulley mainly in cars which were used on winter salty roads. Since over time the inner part of the pulley will rust out and separate from the outer part. In this case the accessory belt will jump off so this will obviously leave you stranded.
-it’s good to keep in mind that the high pressure fuel pump has a separate belt and a tensioner. Most of the owners don’t even know that there is a separate belt for the high pressure fuel pump, so it’s good to replace these two parts preventively.
-if you are buying a car which has around 300 000 km then be prepared to replace the alternator since its lifetime is approximately the already mentioned 300 000 km
-next, the injectors can be faulty on both of these engines but usually just after 200 000 km. Of course they can last way over 300 000 km as well, but this depends on many different things. But all you need to know is that if you got faulty injectors then you can most of the time notice a couple of signs like the: occasional light grey smoke from the exhaust while acceleration or at idle, issues with starting the engine or also a slightly bouncing idle when the engine is warmed up.
-of course oil leaks are also gonna occur but mostly after 200 000 km or 300 000 km. And because of the lack of space they are more expensive to fix on the 4.2 l TDI.
-lastly, the turbochargers are also gonna fail, but usually just in high mileage cars (after 300 000 km), but on more abused cars obviously earlier. Replacing the turbocharger on the 3.0 TDI is not hard, but the 4.2 l TDI has two turbochargers on the sides of the engine and to replace them you have to remove the whole fuckin engine.
4.0 TDI V8 ?
But what about the older 4.0l TDI V8? Well, I would not recommend it even though it looks pretty similar to the 4.2l TDI. But it’s just not worth it since it can have more often issues with the timing chain mechanism even at 200 000 km, it also has the variable intake manifold flap mechanism which is different than on the other two engines, but it doesn’t fucking matter if it’s different since it will of course fail too + the 2 turbochargers are gonna fail too and you have to remove the engine to replace them, injectors are gonna fail too, the crankshaft pulley is gonna fall apart like on the 3.0 TDI, it has 2 ECU-s and overall it’s a bit more mechanic unfriendly engine than the 4.2 TDI. (all of these issues can a lot of times occur around 200 000 km, so earlier than on the other 2 engines. But I’m not saying that this engine can’t reach 300 000 km or 400 000 km without some of these major issues, however there is a much higher chance that it won’t)
+keep in mind that the coolant tank can crack and leak coolant even in cars with the diesel engines
Timing chain
All the engines are equipped with timing chains except the older 3.0l V6, 3.7l V8 and 4.2l V8 petrol engines which have timing belts-which you should change every 120 000 km with the water pump, pulleys and pulley screws.
On the other side the timing chain mechanism is usually fine at least up to approximately 300 000 km. However sometimes it can get worn much earlier-mainly the tensioners, but mostly on the petrol engines and on the 4.0l V8 diesel engine. So check for a short rattle at cold start and keep in mind that you have to remove the whole engine to change that damn chain mechanism.
Transmissions
This A8 can be equipped with 2 types of automatic transmissions.
-Most of these cars are equipped with the regular 6 speed Tiptronic which is mostly reliable. However after 250 000 km the torque converter can be more worn mainly if the previous owner never changed the gearbox fluid. + if you are buying the more powerful S8, W12 or the diesel V8 models then keep in mind that they are more prone to have issues with the gearbox sometimes even before 200 000 km-requiring a repair or rebuild. This phenomenon is caused by the more enthusiastic driving style of the owners, lack of oil changes and because of the bigger stress on the gearbox caused by these powerful engines.
-Then there is the more rare Multitronic CVT gearbox which is still not very reliable, although with regular oil changes and with a regular/not aggressive driving style it should withstand 200 000 km. But of course after this mileage point the lifetime of the gearbox starts to be questionable. (the Multitronic was available ONLY in front wheel drive cars)
If you really want the Multitronic gearbox then at least check it properly before buying. If it’s shuddering or if it’s not working completely smoothly then find another car.
quattro 4WD
Most of these cars are equipped with Quattro which is still that good, old school mechanical and reliable 4wd system so it usually doesn’t have issues even in high mileage cars. Although it’s of course good to occasionally at least change the oil in the front and rear differentials, because mainly in the S8, W12 or V8 diesel engine models they are under a bigger stress so they can get worn and develop noises.
damn power steering fluid
Lastly it’s pretty damn important to check the power steering fluid level regularly and also replace the fluid to at least miminize issues with the power steering system and to extend the lifetime of the pump and the rack. Since there are more and more cases of worn power steering pumps causing whining noises + leaking steering racks and leaking power steering hoses can occur too, so check all this shit before buying.
On the S8 version there is a common power steering return hose which will fail sooner or later = and leak power steering fluid, for more informations about this check out this link.
To summarize things up: the most reliable and most reasonable engines are the older 4.2l V8 petrol and the 3.0l TDI diesel engine. But if you have more money for the repairs then the W12 petrol engine or the 4.2 l TDI are pretty damn good choices as well. Obviously if you have enough money or you can fix the car yourself then you can buy whatever you want even an S8 with monkeys and gnomes inside, but it’s not really worth it.
Then as usual:
- find a good independent mechanic
- avoid cars with performance upgrades
- and keep approximately 5 000 € for the possible repairs
If you have personal experience with this car or more information about it, then you can write it into comments!
